The effect of prolonged interval and continuous exercise in the heat on circulatory markers of intestinal barrier integrity

Purpose The purpose of this study was to determine the effect of prolonged high-intensity interval (INT) and moderate-intensity continuous (CONT) treadmill exercise in the heat on markers of enterocyte injury and bacterial endotoxin translocation. Methods Nine males completed 2 h of work-matched exercise in the heat (40 °C and 15% RH) as either INT (2 min at 80% VO 2 max and 3 min at 30% VO 2 max) or CONT (~ 50% of VO 2 max). Blood samples collected pre- and post-exercise were assayed for intestinal fatty acid-binding protein (I-FABP), claudin-3 (CLDN-3), and lipopolysaccharide-binding protein (LBP). Results I-FABP was significantly increased from pre- to post-exercise in CONT (913.96 ± 625.13 to 1477.26 ± 760.99 pg•mL −1 ; p = 0.014, d = 0.766) and INT (714.59 ± 470.27 to 1547.93 ± 760.99 pg•mL −1 ; p = 0.001, d = 1.160). Pre- to post-exercise changes in I-FABP were not different between CONT and INT ( p = 0.088, d = 0.414). LBP was significantly increased from pre- to post-exercise in INT (15.94 ± 2.90 to 17.35 ± 3.26 μg•mL −1 ; p = 0.028, d = 0.459) but not CONT (18.11 ± 5.35 to 16.93 ± 5.39 μg•mL −1 ; p = 0.070, d = 0.226), and pre- to post-exercise changes in LBP were higher in the INT compared to CONT ( p 0.05). Conclusions We conclude that prolonged exercise in the heat induces enterocyte injury, but interval (or intermittent) exercise may cause greater bacterial endotoxin translocation which may increase the risk for local and systemic inflammation.